Non-obstructive azoospermia (NOA), a lack of sperm in the ejaculate due to defective spermatogenesis, affects as many as 100,000 men in the US, and represents an unmet medical need because many of these men would like to father children, but cannot without surgical intervention. Current therapy for such men is suboptimal, because it relies upon microsurgical testicular sperm extraction (micro-TESE), which at best is successful in obtaining viable sperm 50% of the time in these NOA patients. Unasper Inc. was founded to address this unmet medical need, and consists of a consortium of experienced physician-scientists in male reproduction and infertility, a prominent academic entrepreneur with a research focus in development of optical imaging systems, and a urologic surgeon with significant clinical expertise in fertility and practical experience in isolating sperm from men with NOA. Here Unasper proposes to complete development, testing and validation of an Optical Coherence Tomographic (OCT) system specifically designed to visualize sperm in the testis using a chemotherapy induced model of NOA in rats. We propose two AIMS: AIM 1: Complete the development, testing and validation of OCT technology for intraoperative detection of sperm in NOA testis. Our prior work with optical imaging systems combined with our prior experience using an OCT system during acquisition of the preliminary data for this proposal allows us to readily design a 2-Stage OCT system in the visible range customized for this purpose. This optimized system involves minor modifications of our existing experimental systems and can be built within 5 months at low cost. AIM 2: Test and validate our customized 2-Stage OCT technology in rat NOA testis. Using our 2-Stage OCT in a rat model of induced NOA, we will assess the sensitivity, specificity, and preliminary safety of our technology to detect occult sperm pockets in rat NOA testes. Successful attainment of our OCT technology allowing safe, statistically significant superiority (sensitivity and specificity) of our system over visual assessment of tubules under the dissecting microscope will justify further commercialization, where we will test safety in human sperm and clinical (patients with NOA) feasibility, and plan for regulatory approval for our 2-Stage OCT system. This will represent a clinically significant major advance in how we currently help azoospermic men with NOA who wish to father children using IVF.